1. Field of the Invention
The present invention relates to a process of electroforming a metal product, more particularly a screen, by subjecting a first thin product skeleton formed upon a matrix in a first electrolytic bath and subsequently stripped from the matrix, to an electrolysis in a second electrolytic bath, comprising at least one organic compound improving the growth of metal in a direction substantially perpendicular to the plane of the skeleton.
2. Description of the Prior Art
A process of this type for electrolytically forming a screen has been used in the art and is disclosed in NL. S No. 80,021,97. In this known process a first thin screen skeleton is formed by electrodepositing nickel metal upon the ribs of a steel plate comprising recesses filled with a di-electric material, e.g. bituminous material. Prior to stripping the formed first screen skeleton from the matrix and to facilitate said stripping, the separating ribs are provided with a layer of beeswax as a separating means.
Thereupon said first thin screen skeleton is thickened in a second electrolytic bath at least comprising one organic compound to improve a metal growth, in a direction substantially perpendicular to the plane of the screen to obtain the desired screen.
The screen as formed suffers from a number of drawbacks, getting the more serious in case of more or less differing properties between the deposited metal layer and the screen skeleton, but even when identical metals are being used, the following shortcomings will arise:
(a) The final screen has an a-symmetrical building up of materials, resulting in different properties inherent therewith, such as ductility and corrosion resistance. In addition thereto the optical appearance of said screens is imperfect;
(b) the mechanical resistance of the screen is extremely small if soft types of metals have been used for one of the two layers.
It should also be noted that it is known per se from NL. S No. 70,024,67 to electroform a screen by depositing a first metal upon a matrix in a first electrolytic bath and to subsequently deposit thereon a second metal in a second electrolytic bath, said metals differing from each other. Said Patent Application No. 70,024,67 describes the use of soft metals for this purpose, the thickness of the obtained screen consisting for 25% to 75% of hard metal.
Apart from the fact that no use is made in this known process of at least three electrolytic baths, in addition a thin product skeleton as deposited upon a matrix in a first electrolytic bath is not strippd from the matrix prior to subjecting the obtained first thin skeleton to an electrolysis in a second electrolytic bath. As a result products, and more particularly screens, in which an optimum metal growth occurs, in a direction substantially perpendicular to the skeleton, cannot possibly be obtained.